High volume conveyor systems are used in mines to move crushed mining products such as crushed rock, minerals, coal and/or ores. Such conveyor systems typically have a wide material-carrying conveyor belt supported by a large number of rollers spaced apart along the length of the conveyor system. The conveyor system may extend for as much as several miles. If the conveyor system extends down a slope the conveyor belt may be driven by the weight of material piled on the top surface of the conveyor belt. The conveyor belt may also be driven by a motor coupled either to one or more of the rollers supporting the conveyor belt or to the conveyor belt itself, particularly where the conveyor system does not extend down a slope.
In a conveyor system which descends down a slope the material on the conveyor belt exerts a force on the conveyor belt which tends to accelerate the conveyor belt. In a typical conveyor system, brakes must be provided to prevent the conveyor belt from running too quickly. To prevent excessive acceleration of the conveyor belt, the brakes and friction present in the conveyor system must dissipate an amount of energy proportional to the change in potential energy of the material being moved by the conveyor system. The potential energy of the many tons of rock at the top of the conveyor system can be substantial.
Moritake, U.S. Pat. No. 3,713,521 discloses a braking system for a roller in a beltless conveyor. The braking system comprises an electrical generator and brake inside a conveyor roller. Electricity generated by the generator activates an electromagnetic brake inside the roller. All of the electrical power generated by Moritake's generator is used to operate the electromagnetic brake or is dissipated in a variable resistor which may be used to vary the braking force.
Giconi, U.S. Pat. No. 3,987,307, discloses a system for generating electrical energy by dropping particulate material down a shaft and directing the falling particulate matter into buckets around the periphery of a large wheel, similar to a "water wheel". The wheel turns as a result of the transference of kinetic energy from the falling particulate matter to the wheel and the unbalanced weight of particulate matter on the wheel. The hub of the wheel is coupled to an electrical generator.